The present invention relates to an apparatus for automatically developing patterns that have been written, and a method for developing using the apparatus.
Known is art (such as Japanese Patent Laid Open No. 135838-1987) for immersing an electroconductive body upon which a predetermined pattern has been written on a resist film applied to a surface of that body, is placed in a solution of developer and containing an electrode, and then the value of the current that flows between the electrconductive body and the electrode is used as the basis for then determining the point at which developing of the written pattern is completed. In this art, an organic solvent in which an electrolytic substance has been added (such as methylisobutylketone containing a solution of 1 mM (mili Moll) tetrabutyl ammonium perchlorate) is used as the developing solution. In addition, MODEL-MX-1000N of Nagase Sangyo (K.K.) is one example of two liquids mixing system that is used for adding an electrolytic substance into an organic solvent or a developing solution.
In such developing solutions as these, when the electrode and the conductor upon which a pattern has been written, are immersed in the solution, the current that flows between the electroconductive body and the electrode shows a clear peak or peaks and so this peak is used to determine when the developing of the written pattern has been completed.
For an example, there is given a substrates upon which a plurality of patterns have been written, such as a photomask where chrome has been vapor-deposited onto a quartz base plate and then PMMA (polymethylmethacrylate) has been applied as the electron beam resist and patterns with 2 .mu.m lines and spaces, patterns with 25 .mu.m lines and spaces, and patterns with 100 .mu.m lines and spaces are written on this PMMA. When developing using the above technologies is performed for this electroconductive substrate, the current that flows between the electrode and the electroconductive body is shown by 1.sub.1 of FIG. 4. This is to say that the respective peaks of A, B and C appear for patterns of 100 .mu.m, 25 .mu.m and 2 .mu.m. Accordingly, if the point at which developing is completed is determined by simply using the peak as is performed using conventional art, point A is mistakenly determined at the point at which developing is completed despite the fact that the point at which developing is actually completed should be point C, as shown in FIG. 4, and thereby causes the problem of a resultant drop in the dimensional accuracy of the pattern.
This problem occurs because the developing solution itself has a high resistance and this causes charging of electrons resulting two electrical layers. This phenomenon often occurs when the sensitivity of the developing solution is raised too high.